MPLS is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses. In an MPLS network, data packets are assigned labels. Packet-forwarding decisions are made solely on the contents of this label. This allows one to create end-to-end virtual circuits across any type of transport medium, using any protocol.
In MPLS network, routers that perform routing based only on the label are called label switch routers (LSRs). The entry and exit points of an MPLS network are called label edge routers (LERs). Labels are distributed between LERs and LSRs using the label signaling mechanisms, such as Label Distribution Protocol (LDP) and Resource Reservation Protocol-Traffic Engineering (RSVP-TE). Label-switched paths (LSPs) are established for a variety of purposes, such as to create the Virtual Private Networks (VPNs) connecting the geographically distributed sites or to route traffic along specified paths.
For a specific MPLS-based VPN, LERs that function as ingress and/or egress routers to the VPN are often called PE (Provider Edge) routers. Devices that function only as transit routers are similarly called P (Provider) routers.
Nowadays, the telecommunication operators increasingly establish MPLS multicast tree to deliver the traffics, such as Internet Protocol Television (IPTV) program, online gaming etc, to the end users. FIG. 1 illustrates the multicast tree for Virtual Private Local Area Network Service (VPLS), which connects the PEs through the point-to-multipoint (P2MP) LSPs. In order to reduce the operating expense and capital expense, the operators prefer the deployment of static MPLS or MPLS-TP in their backhaul networks. Take the static VPLS as example, the local multicast group forwarding table stored in leaf node (e.g. PE2, PE4) need to be configured and updated manually by using the network management system. In particular, the manual configuration is accomplished through the pseudo-wires (PWs) in the full meshed PW network among all the PEs. In addition, it is impossible for the existing solution to configure the local multicast forwarding table in the transit node, i.e. LSRs, due to the use of the PW, because the PW directly wired between the PEs is transparent to the transit nodes. And for the same reasons, the root node (e.g. PE1) needs replicate the multicast group configuration packet for all the leaf nodes and relay to them, which causes the low performance of delivery.